Substrate processing apparatus and method

ABSTRACT

A substrate processing apparatus can perform an electrolytic processing, which is different from a common, conventional etching, to remove (clean off) a conductive material (film) formed on or adhering to a bevel portion, etc. of a substrate, or process a peripheral portion of a substrate through an electrochemical action. The substrate processing apparatus includes: an electrode section having a plurality of electrodes which are laminated with insulators being interposed, and having a holding portion which is to be opposed to a peripheral portion of a substrate; an ion exchanger disposed in the holding portion of the electrode section; a liquid supply section for supplying a liquid to the holding position of the electrode section; and a power source for applying a voltage to the electrodes of the electrode section so that the electrodes alternately have different polarities.

TECHNICAL FIELD

This invention relates to a substrate processing apparatus and method,and more particularly to a substrate processing apparatus and methodwhich can be utilized as a bevel-removal apparatus for processing aconductive material or removing impurities adhering to a peripheralportion (bevel portion or edge portion) of a substrate, such as asemiconductor wafer, or which can be used for carrying out processing toremove a film formed on the surface of a substrate by a predeterminedthickness.

BACKGROUND ART

In recent years, instead of using aluminum or aluminum alloys as amaterial for forming interconnection circuits on a substrate such as asemiconductor wafer, there is an eminent movement towards using copper(Cu) which has a low electric resistance and high electromigrationresistance. Copper interconnects are generally formed by filling copperinto fine recesses formed in a surface of a substrate. There are knownvarious techniques for forming such copper interconnects, including CVD,sputtering, and plating. According to any such technique, a copper filmis formed on the substantially entire surface of a substrate, followedby removal of unnecessary copper by chemical mechanical polishing (CMP).

FIGS. 13A through 13C illustrate, in sequence of process steps, anexample of forming such a substrate W having copper interconnects. Asshown in FIG. 13A, an insulating film 2, such as a silicon oxide film ofSiO₂ or a film of low-k material, is deposited on a conductive layer 1 ain which electronic devices are formed, which is formed on asemiconductor base 1. A contact hole 3 and a trench 4 for interconnectsare formed in the insulating film 2 by the lithography and etchingtechnique. Thereafter, a barrier layer 5 of TaN or the like is formed onthe entire surface, and a seed layer 7 as an electric supply layer forelectroplating is formed on the barrier layer 5.

Then, as shown in FIG. 13B, copper plating is performed onto the surfaceof the substrate W to fill the contact hole 3 and the trench 4 withcopper and, at the same time, deposit a copper film 6 on the insulatingfilm 2. Thereafter, the copper film 6 and the barrier layer 5 on theinsulating film 2 is removed by chemical mechanical polishing (CMP) soas to make the surface of the copper film 6 filled in the contact hole 3and the trench 4 for interconnects and the surface of the insulatingfilm 2 lie substantially on the same plane. An interconnection composedof the copper film 6 as shown in FIG. 13C is thus formed.

In this case, the barrier layer 5 is formed so as to cover thesubstantially entire surface of the insulating film 2, and the seedlayer 7 is also formed so as to cover the substantially entire surfaceof the barrier layer 5. Thus, in some cases, a copper film that is theseed layer 7 resides on a bevel (outer peripheral portion) of thesubstrate W, or copper is deposited on an edge (outer peripheralportion), which is inward of the bevel of the substrate W, and remainsunpolished. Copper can easily be diffused into the insulating film in asemiconductor fabrication process such as annealing, thus deterioratingthe electric insulation of the insulating film, and may cause crosscontamination in subsequent processes of delivering, storing andprocessing the substrate. For these reasons, it is necessary that theremaining deposited copper on the peripheral portion of the substrateshould be completely removed. Therefore, it is suggested that conductivematerial such as copper deposited on or adhering to the peripheralportion of the substrate will be removed by an etching process or thelike.

As described above, the impurity contamination in the production of asemiconductor device greatly affects the reliability of thesemiconductor device. Accordingly, with respect to a substrate in whicha film has been formed e.g. by plating over the entire surface e.g. forthe formation of semiconductor interconnects or contacts, the substrateis usually subjected to a process for removing the film on a peripheralportion of the substrate in order to prevent a later contamination of aprocessing device which would be caused by contact between the film anda substrate transport device. Such a film removal processing hasgenerally been carried out by supplying an etching liquid only to ato-be-removed region of a substrate to effect removal of a film only inthe to-be-removed region.

Components in various types of equipment have recently become finer andhave required higher accuracy. As sub-micro manufacturing technology hascommonly been used, the properties of materials are largely influencedby the processing method. Under these circumstances, in such aconventional machining method that a desired portion in a workpiece isphysically destroyed and removed from the surface thereof by a tool, alarge number of defects may be produced to deteriorate the properties ofthe workpiece. Therefore, it becomes important to perform processingwithout deteriorating the properties of the materials.

Some processing methods, such as chemical polishing, electrolyticprocessing, and electrolytic polishing, have been developed in order tosolve this problem. In contrast with the conventional physicalprocessing, these methods perform removal processing or the like throughchemical dissolution reaction. Therefore, these methods do not sufferfrom defects, such as formation of an altered layer and dislocation, dueto plastic deformation, so that processing can be performed withoutdeteriorating the properties of the materials.

When removing a conductive material, such as copper, by e.g. a commonetching processing technique conventionally employed, a chemical liquid,selected from a variety of kinds, is used. This requires an adequatepost-cleaning and, in addition, imposes a considerable load upon wasteliquid treatment. Also in this connection, it is to be pointed out thatthough a low-k material, which has a low dielectric constant, isexpected to be predominantly used in the future as a material for theinsulating film of a semiconductor substrate, the low-k material has alow mechanical strength and therefore is hard to endure the stressapplied during CMP processing.

Further, with such an etching processing (film-removing processing),control of an etching width and of an edge configuration cannot be madewith ease. In addition, with the progress towards multi-layeredinterconnects, there is the problem of an increased number of processsteps becoming necessary.

A method has been reported which performs CMP processing simultaneouslywith plating, viz. chemical mechanical electrolytic polishing. Accordingto this method, the mechanical processing is carried out to the growingsurface of a plating film, causing the problem of denaturing of theresulting film.

In the case of the above-mentioned conventional electrolytic processingor electrolytic polishing, the process proceeds through anelectrochemical interaction between a workpiece and an electrolyticsolution (aqueous solution of NaCl, NaNO₃, HF, HCl, HNO₃, NaOH, etc.).Since an electrolytic solution containing such an electrolyte must beused, contamination of a workpiece with the electrolyte cannot beavoided.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above situation inthe related art. It is therefore a first object of the present inventionto provide a substrate processing apparatus and method that can performan electrolytic processing through an electrochemical action, which isdifferent from a common, conventional etching, to remove (clean off) aconductive material (film) formed on or adhering to a bevel portion,etc. of a substrate.

It is a second object of the present invention to provide a substrateprocessing apparatus and method that can simplify removal of a film in aperipheral portion of a substrate and can securely remove the film.

In order to achieve the above objects, the present invention provides asubstrate processing apparatus comprising: an electrode section having aplurality of electrodes which are laminated with insulators beinginterposed, and having a holding portion which is to be opposed to aperipheral portion of a substrate; a liquid supply section for supplyinga liquid to the holding position of the electrode section; and a powersource for applying a voltage to the electrodes of the electrode sectionso that the electrodes alternately have different polarities.

An ion exchanger may be disposed in the holding portion of the electrodesection.

FIG. 1 illustrates the principle of electrolytic processing effected inthe above electrolytic processing apparatus. FIG. 1 shows the ionicstate in the electrolytic processing apparatus when an ion exchanger 12a mounted on a processing electrode 14 (e.g. cathode) and an ionexchanger 12 b mounted on a feeding electrode 16 (e.g. anode) arebrought into contact with or close to a surface of a workpiece(substrate) 10, while a voltage is applied via a power source 17 betweenthe processing electrode 14 and the feeding electrode 16, and a liquid18, e.g. ultrapure water, is supplied from a liquid supply section 19between the processing electrode 14, the feeding electrode 16 and theworkpiece 10.

When a liquid like ultrapure water that in itself has a largeresistivity is used, it is preferred to bring the ion exchanger 12 ainto contact with the surface of the workpiece 10. This can lower theelectric resistance, lower the requisite voltage and reduce the powerconsumption. The “contact” in the present electrolytic processing doesnot imply “press” for giving a physical energy (stress) to a workpieceas in CMP.

Water molecules 20 in the liquid 18 such as ultrapure water aredissociated using the ion exchangers 12 a, 12 b into hydroxide ions 22and hydrogen ions 24 effectively. The hydroxide ions 22 thus produced,for example, are carried, by the electric field between the workpiece 10and the processing electrode 14 and by the flow of the liquid 18, to thesurface of the workpiece 10 opposite to the processing electrode 14whereby the density of the hydroxide ions 22 in the vicinity of theworkpiece 10 is enhanced, and the hydroxide ions 22 react with the atoms10 a of the workpiece 10. The reaction product 26 produced by thisreaction is removed from the workpiece 10 by the flow of the liquid 18along the surface of the workpiece 10. Removal processing of the surfaceof the workpiece 10 is thus effected.

As will be appreciated from the above, the removal processing accordingto the present invention is effected purely by the electrochemicalinteraction between the reactant ions and the workpiece. The presentelectrolytic processing thus clearly differs in the processing principlefrom CMP according to which processing is effected by the combination ofthe physical interaction between an abrasive and a workpiece, and thechemical interaction between a chemical species in a polishing liquidand the workpiece.

The ion exchanger may be a laminate of a plurality of ion-exchangematerials.

By making the ion exchanger a multi-layer structure consisting oflaminated layers of ion-exchange materials, such as ion-exchange fibersand an ion-exchange membrane, it is possible to increase the total ionexchange capacity whereby formation of an oxide, for example in removal(polishing) processing of copper, can be restrained to thereby avoid theoxide adversely affecting the processing rate. Further, by using a softion-exchange material, such as a porous membrane or a woven fabric, forthe outermost layer of a multi-layer ion exchanger, the occurrence of anabnormal processing, such as rise-up or pealing of a copper film afterprocessing, can be suppressed.

The ion exchanger may have water-absorbing properties. This allows aliquid such as ultrapure water to flow within the ion exchanger.

The ion exchanger may have one or both of an anion-exchange ability anda cation-exchange ability. An ion exchanger having an anion-exchangeability and an ion exchanger having a cation-exchange ability can beused selectively according to a substrate. The use of an ion-exchangerhaving both of anion-exchange and cation-exchange abilities can broadenthe range of processible materials and, in addition, can prevent theformation of impurities due to the polarity.

The liquid may be pure water, a liquid having an electric conductivity(referring herein to that at 25° C., 1 atm) of not more than 500 μS/cm,or an electrolytic solution.

Pure water is a water having an electric conductivity of not more than10 μS/cm. The use of pure water in electrolytic processing enables aclean processing without leaving impurities on the processed surface ofa workpiece, whereby a cleaning step after the electrolytic processingcan be simplified. Specifically, one or two-stages of cleaning maysuffice after the electrolytic processing.

It is also possible to use a liquid obtained by adding an additive, suchas a surfactant, to pure water or ultrapure water, and having anelectric conductivity of not more than 500 μS/cm, preferably not morethan 50 μS/cm, more preferably not more than 0.1 μS/cm (resistivity ofnot less than 10 MΩ·cm). Such a low electric conductive liquid can forma layer, which functions to inhibit ion migration evenly, at theinterface between a workpiece (e.g. substrate) and an ion exchanger,thereby moderating concentration of ion exchange (metal dissolution) toenhance the flatness of the processed surface.

The additive plays a role to prevent local concentration of ions (e.g.hydroxide ions (OH⁻)). It is noted in this regard that “an equalprocessing (removal) rate at various points over the entire processingsurface” is an important factor for providing a flat processed surface.When a single electrochemical removal reaction is in progress, a localdifference in the processing removal rate may be produced by a localconcentration of reactant ions. The local concentration of reactant ionsmay be caused mainly by a deviation in the electric field intensitybetween the processing electrode and the feeding electrode, and adeviation in the distribution of reactant ions in the vicinity of thesurface of a workpiece. The local concentration of reactant ions can beprevented by allowing the additive, which plays a role to prevent localconcentration of ions (e.g. hydroxide ions), to exist between aworkpiece and an ion exchanger.

An aqueous solution of a neutral salt such as NaCl or Na₂SO₄, an acidsuch as HCl or H₂SO₄, or an alkali such as ammonia may be used as theelectrolytic solution, and may be properly selected according to theproperties of a workpiece. When using electrolytic solution, it isbetter to use the low concentration electrolytic solution which electricconductivity is not more than 500 μS/cm, to avoid much contamination.

Ultrapure water is preferably used as the liquid. By “ultrapure water”is herein meant a water having an electric conductivity of not more than0.1 μS/cm. The use of ultrapure water enables a cleaner processingwithout leaving impurities on the processed surface of a workpiece.

The electrode section may be disposed in a tilted state relative to ahorizontal plane so that the substrate can roll over the ion exchangerdisposed in the holding portion of the electrode section and move alongthe electrode section.

The present invention also provides a substrate processing methodcomprising: opposing a peripheral portion of a substrate to a holdingportion provided in an electrode section having a plurality ofelectrodes which are laminated with insulators being interposed;supplying a liquid to the holding portion of the electrode section; andapplying a voltage to the electrodes of the electrode section so thatthe electrodes alternately have different polarities.

An ion exchanger may be disposed in the holding portion of the electrodesection.

The present invention also provides another substrate processingapparatus for processing a substrate, comprising: a processing toolfacing across a first film and a second film for removing the first filmand the second film simultaneously from an entire surface of asubstrate, wherein the first film is formed on the surface of thesubstrate, and the second film is formed on the first film so as to forma step between a peripheral portion and an effective device portion ofthe substrate by the first film and the second film. The predeterminedthickness may be at least the thickness of the film 7 in the peripheralportion 532 (see FIGS. 7A and 7B).

The substrate processing apparatus can perform in a simple manner aneffective removal processing of a substrate W, for example, a substrateW as shown in FIGS. 7A and 7B, in which a film is formed in thesubstrate surface WA such that the film has a step between theperipheral portion 532 and the effective device portion 533 of thesubstrate, thereby removing the film 6, 7 in the substrate surface WA bya predetermined thickness t over the entire surface simultaneously, andcompletely removing the film 7 in the peripheral portion 532 whileleaving the film 6 in the effective device portion 533. Preferably, thesubstrate processing apparatus can remove the film 6, 7 in the substratesurface WA simultaneously over the entire surface by a predetermineduniform thickness.

The substrate processing apparatus may comprise an electrolyticprocessing apparatus. Such a substrate processing apparatus, because ofan electrolytic processing apparatus, can produce a high-qualitysubstrate having a high flatness without defects in the substratesurface, such as a denatured layer and transformation, caused by plasticdeformation.

According to one embodiment, as shown in FIG. 9, the substrateprocessing apparatus as an electrolytic processing apparatus comprises:a processing electrode 218 brought into contact with or close to asubstrate W; a feeding electrode 236 for feeding electricity to thesubstrate W; an ion exchanger 235 disposed in at least one of the spacebetween the substrate W and the processing electrode 218, and the spacebetween the substrate W and the feeding electrode 236; a fluid supplysection 229, 217, 219, 220, 228 for supplying a fluid 202 between thesubstrate W and the ion exchanger 235; and a power source 223 forapplying a voltage between the processing electrode 218 and the feedingelectrode 236.

According to this substrate processing apparatus, with the provision ofthe processing electrode 218, the feeding electrode 236, the ionexchanger 235 and the power source 223, electrolytic processing of asubstrate W proceeds through the electrochemical action described below.

When the fluid 202 is a liquid, for example pure water, water isdissociated into hydroxide ions and hydrogen ions by the application ofa voltage between the processing electrode 218 and the feeding electrode236. The dissociation of water is promoted by the ion exchanger 235. Bythe electric field between the substrate W and the processing electrode218, and by the flow of pure water 202 supplied between the substrate Wand the ion exchanger 235, the hydroxide ions produced by the waterdissociation are moved to the surface WA, facing the processingelectrode 218, of the substrate W. The density of hydroxide ions thusincreases in the vicinity of the substrate surface WA, whereby reactionbetween the atoms of the surface WA and hydroxide ions occurs. Thereaction product of this reaction dissolves in pure water 202 and isremoved from the substrate W, while some of the product accumulates inthe ion exchanger 235. Removal processing of the surface WA of thesubstrate W is thus effected. Since the surface WA facing the processingelectrode 218 is processed, by moving the processing electrode 218 alongthe surface WA of the substrate W, the surface WA can be removed by adesired thickness or processed into a desired surface configuration.

The ion exchanger may be of a single-layer structure or of a multi-layerlaminated structure. The use of a multi-layer laminated structure makesit possible to use a thin membrane as one ion exchanger and increasesthe total ion exchange capacity. The kinds or properties of ionexchangers may be varied for every layer. For example, the hardness maybe varied for every layer.

The power source may apply a predetermined voltage or a controlledvoltage that allows a constant electric current to flow. Thisfacilitates control of the processing amount (processing thickness) orthe end point of processing. Typically, the object to be processed is afilm formed in the substrate surface WA.

According to another embodiment, as shown in FIG. 6, the substrateprocessing apparatus as an electrolytic processing apparatus comprises:a processing electrode 518 brought into contact with or close to asubstrate W; a feeding electrode for feeding electricity to thesubstrate W; a fluid supply section 529, 517, 519, 520, 528 forsupplying a fluid 502 to at least one of the space between the substrateW and the processing electrode 518, and the space between the substrateW and the feeding electrode; and a power source 523 for applying avoltage between the processing electrode 518 and the feeding electrode(substrate W, connected to the power source 523).

According to this substrate processing apparatus, with the provision ofthe processing electrode 518, the feeding electrode (substrate W) andthe power source 523, electrolytic processing of a substrate W proceedsthrough the electrochemical action as described below.

When the fluid 502 is a liquid, for example pure water, water isdissociated into hydroxide ions and hydrogen ions by the application ofa voltage between the processing electrode 518 and the feeding electrode(substrate W). By the electric field between the substrate W and theprocessing electrode 518 and by the flow of pure water 502 suppliedbetween the substrate W and the processing electrode 518 and/or betweenthe substrate W and the feeding electrode, the hydroxide ions producedby the water dissociation are moved to the surface WA, facing theprocessing electrode 518, of the substrate W. The density of hydroxideions thus increases in the vicinity of the substrate surface WA, wherebyreaction between the atoms of the surface WA and hydroxide ions occurs.The reaction product of this reaction dissolves in pure water 502 and isremoved from the substrate W. Removal processing of the surface WA ofthe substrate W is thus effected. Since the surface WA facing theprocessing electrode 518 is processed, by relatively moving theprocessing electrode 518 along the surface WA of the substrate W, thesurface WA can be removed by a desired thickness or processed into adesired surface configuration.

In the substrate processing apparatus of the present invention, forexample the substrate processing apparatus shown in FIG. 9, the use ofan electrolysis solution as a fluid 202 can enhance the processing rate.When a liquid having an electric conductivity of not more than 500 μS/cmis used as the fluid 202, through the processing rate may be lowered ascompared to the use of an electrolysis solution, processing can beperformed with the liquid containing less impurity. The use of purewater enables a cleaner processing. Even when using pure water or aliquid having an electric conductivity of not more than 500 μS/cm, theprocessing rate can be maintained at a high level by the provision ofthe ion exchanger 235.

According to still another embodiment of the present invention, as shownin FIG. 8, the substrate processing apparatus as an electrolyticprocessing apparatus comprises: a processing electrode 118 brought intocontact with or close to a substrate W; a feeding electrode (substrateW, connected to the power source 123) for feeding electricity to thesubstrate W; a fluid supply section for supplying a fluid 102 which ispure water or a liquid having an electric conductivity of not more than500 μS/cm; a power source 123 for applying a voltage between theprocessing electrode 118 and the feeding electrode (substrate W); and anion exchanger 135.

According to this substrate processing apparatus, with the provision ofthe processing electrode 118, the feeding electrode (substrate W), theion exchanger 135 and the power source 123, electrolytic processing of asubstrate W proceeds through the electrochemical action described below.

Water is dissociated into hydroxide ions and hydrogen ions by theapplication of a voltage between the processing electrode 118 and thefeeding electrode (substrate W). The dissociation of water is promotedby the ion exchanger 135. By the electric field between the substrate Wand the processing electrode 118 and by the flow of pure water 102 orthe liquid 102 supplied, the hydroxide ions produced by the waterdissociation are moved to the surface WA, facing the processingelectrode 118, of the substrate W. The density of hydroxide ions thusincreases in the vicinity of the substrate surface WA, whereby reactionbetween the atoms of the surface WA and hydroxide ions occurs. Thereaction product of this reaction dissolves in pure water 102 or in theliquid 102 and is removed from the substrate W, while some of theproduct accumulates in the ion exchanger 135. Removal processing of thesurface WA of the substrate W is thus effected. Since the surface WAfacing the processing electrode 118 is processed, by moving theprocessing electrode 118 along the surface WA of the substrate W, thesurface WA can be removed by a desired thickness or processed into adesired surface configuration.

The substrate processing apparatus may comprise a chemical etchingapparatus. Such a substrate processing apparatus, because of a chemicaletching apparatus, can produce a high-quality substrate having a highflatness without defects in the substrate surface, such as a denaturedlayer and transformation, caused by plastic deformation.

The present invention also provides a substrate processing method asillustrated in FIGS. 7A and 7B, comprising: forming a film 6, 7 on asubstrate W such that the film has a step between the peripheral portion532 and the effective device portion 533 of the substrate W; andremoving the film 6, 7 in the substrate surface WA by a predeterminedthickness over the entire surface simultaneously.

The step of forming the film such that the film has a step between theperipheral portion 532 and the effective device portion 533 typicallyconsists of: a first stage of forming a first film 7 over the entiresubstrate surface WA; and a second stage of forming a second film 6 inthe effective device portion 533 of the substrate. The step of removingthe film 6, 7 in the substrate surface WA by a predetermined thicknessover the entire surface simultaneously may be carried out in such amanner that the film 6, 7 in the substrate surface WA is processed at auniform processing rate over the entire surface WA until the first film7 in the peripheral portion 532 is completely removed. The processingmay be terminated at the time when the film 7 is completely removed.Since the film has a step between the peripheral portion 532 and theeffective device portion 533, even when the first film 7 in theperipheral portion 532 is completely removed, the second film 6 in theeffective device portion 533 still remains. The film 7 in the peripheralportion 532 can thus be selectively removed. The processing may beeither by electrolytic processing or by chemical etching processing.

According to a preferred embodiment, the substrate processing method asan electrolytic processing method comprises: forming a first film on thesurface of a substrate, and a second film on the first film so as toform a step between a peripheral portion and an effective device portionof the substrate by the first film and the second film; bringing aprocessing electrode close to a substrate while feeding electricity froma feeding electrode to the substrate; disposing an ion exchanger in atleast one of the space between the substrate and the processingelectrode, and the space between the substrate and the feedingelectrode; supplying a fluid between the substrate and the ionexchanger; and applying a voltage between the processing electrode andthe feeding electrode so as to remove the first film and the second filmsimultaneously from the entire surface of the substrate by apredetermined thickness.

The above and other objects, features, and advantages of the presentinvention will be apparent from the following description when taken inconjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the principle of electrolyticprocessing according to the present invention;

FIG. 2 is a schematic view of an electrolytic processing apparatus(substrate processing apparatus) of one embodiment of the presentinvention, which is utilized as a bevel-removal apparatus;

FIG. 3 is a perspective view of the electrode section of FIG. 2;

FIG. 4 is an enlarged sectional view of the electrode of the electrodesection of FIG. 2;

FIG. 5 is a schematic sectional view of an electrolytic processingapparatus (substrate processing apparatus), utilized as a bevel-removalapparatus, according to another embodiment of the present invention;

FIG. 6 is a schematic sectional view of an electrolytic processingapparatus (substrate processing apparatus) according to still anotherembodiment of the present invention;

FIGS. 7A and 7B are cross-sectional views illustrating a configurationalchange of a substrate when it is processed by the electrolyticprocessing apparatus of FIG. 6;

FIG. 8 is a schematic sectional view of an electrolytic processingapparatus (substrate processing apparatus) according to still anotherembodiment of the present invention;

FIG. 9 is a schematic sectional view of an electrolytic processingapparatus (substrate processing apparatus) according to still anotherembodiment of the present invention;

FIG. 10 is a bottom plan view illustrating the arrangement of theprocessing electrode and the feeding electrode of the electrolyticprocessing apparatus of FIG. 9;

FIG. 11 is a schematic sectional view of a chemical etching apparatus(substrate processing apparatus) according to an embodiment of thepresent invention;

FIG. 12 is a plan view showing a substrate processing system which isprovided with a substrate processing apparatus according to the presentinvention; and

FIGS. 13A through 13C are diagrams illustrating, in sequence of processsteps, the formation of copper interconnects.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will now be described indetail with reference to the drawings. Though the below-describedembodiments refer to substrate processing apparatuses which use asubstrate as a workpiece to be processed and remove (polish) copperformed on or adhering to a peripheral portion (bevel portion or edgeportion) of the substrate, the present invention is of course applicableto processing apparatuses which process a workpiece other than asubstrate.

FIGS. 2 through 4 show an electrolytic processing apparatus (substrateprocessing apparatus) according to an embodiment of the presentinvention, which is utilized as a bevel-removal apparatus. Thebevel-removal apparatus (electrolytic processing apparatus) includes apair of rotatable roller chucks 30 for vertically holding a substrate W,which has been dropped in from above, and an electrode section 32provided below the roller chucks 30.

The roller chucks 30 each have a V-shaped groove in the circumferentialend surface and hold the substrate W by bringing a peripheral portion ofthe substrate into engagement with the groove. Further, the rollerchucks 30 are directly connected to a motor (not shown), and are allowedto rotate synchronously in the same direction by the actuation of themotor, thereby rotating the substrate W.

The electrode section 32 has a plurality of electrodes 36 that areconnected in series with insulators 34 being interposed. The cathode andthe anode of a power source 40 are alternately connected to theelectrodes 36. According to this embodiment, the electrodes 36 connectedto the cathode of the power source 40 become processing electrodes 42,and the electrodes 36 connected to the anode of the power source 40become feeding electrodes 44. This applies to processing of e.g. copper,because electrolytic processing of copper proceeds on the cathode side.Depending upon a material to be processed, the cathode side can be afeeding electrode and the anode side can be a processing electrode. Morespecifically, when the material to be processed is copper, molybdenum,iron or the like, electrolytic processing proceeds on the cathode side,and therefore the electrodes 36 connected to the cathode of the powersource 40 should be the processing electrodes 42 and the electrodes 36connected to the anode of the power source 40 should be the feedingelectrodes 44. In the case of aluminum, silicon or the like, on theother hand, electrolytic processing proceeds on the anode side.Accordingly, the electrodes connected to the anode of the power sourceshould be the processing electrodes and the electrodes connected to thecathode should be the feeding electrodes.

Further, in the upper surface of the electrode section 32, there isprovided a groove 38 as a holding portion, which extends linearly overthe full length in the longitudinal direction of the electrode section32, and which may have a U-shape section in conformity with thesectional configuration of the periphery of the substrate W. The entiresurface of the groove (holding portion) 38 is covered with an ionexchanger 48 that is bent in the U-shape conforming to the surface ofthe groove 38.

The electrode section 32 is located in such a position that when thesubstrate W is held by the roller chucks 30, the lowermost surface ofthe substrate W is close to or in slight contact with the surface of theion exchanger 48 disposed in the groove 38 of the electrode section 32.The groove 38 extends in such a direction that the substrate Wtransverses the lamination of electrodes 36.

Though this embodiment shows the provision in the electrode section 32of the groove 38 which extends linearly across the insulators 34 and theelectrodes 36, it is also possible to provide a groove which extends inan arc in conformity with the peripheral shape of the substrate W, sothat the ion exchanger disposed in the groove can be closed to or inslight contact with the peripheral end surface of the substrate W overthe full length in the longitudinal direction of the ion exchanger.

The “bevel portion” of a substrate (e.g. semiconductor wafer) generallyrefers to a several mm-width region from the peripheral end of thesubstrate. When carrying out removing of a conductive film in such aportion, the portion needs to be “in a covered state”. To meet thisrequirement, the groove 38 as a holding portion is provided in theelectrode section 32, according to this embodiment. As an alternative,it is possible to form a groove by disposing two flat plates so thatthey face each other. It is also possible to make an electrode portionof a flat plate, and press the end of a substrate (e.g. substrate wafer)against the electrode portion by utilizing elasticity of an ionexchanger mounted on the flat plate-shaped electrode section.

The ion exchanger 48 may be a nonwoven fabric which has ananion-exchange ability or a cation-exchange ability. A cation exchangerpreferably carries a strongly acidic cation-exchange group (e.g.sulfonic acid group); however, a cation exchanger carrying a weaklyacidic cation-exchange group (e.g. carboxyl group) may also be used.Though an anion exchanger preferably carries a strongly basicanion-exchange group (e.g. quaternary ammonium group), an anionexchanger carrying a weakly basic anion-exchange group (e.g. tertiary orlower amino group) may also be used.

The nonwoven fabric carrying a strongly basic anion-exchange group canbe prepared by, for example, the following method: A polyolefin nonwovenfabric having a fiber diameter of 20–50 μm and a porosity of about 90%is subjected to the so-called radiation graft polymerization, comprisingγ-ray irradiation onto the nonwoven fabric and the subsequent graftpolymerization, thereby introducing graft chains; and the graft chainsthus introduced are then aminated to introduce quaternary ammoniumgroups thereinto. The capacity of the ion-exchange groups introduced canbe determined by the amount of the graft chains introduced. The graftpolymerization may be conducted by the use of a monomer such as acrylicacid, styrene, glicidyl methacrylate, sodium styrenesulfonate orchloromethylstyrene. The amount of the graft chains can be controlled byadjusting the monomer concentration, the reaction temperature and thereaction time. Thus, the degree of grafting, i.e. the ratio of theweight of the nonwoven fabric after graft polymerization to the weightof the nonwoven fabric before graft polymerization, can be made 500% atits maximum. Consequently, the capacity of the ion-exchange groupsintroduced after graft polymerization can be made 5 meq/g at itsmaximum.

The nonwoven fabric carrying a strongly acidic cation-exchange group canbe prepared by the following method. As in the case of the nonwovenfabric carrying a strongly basic anion-exchange group, a polyolefinnonwoven fabric having a fiber diameter of 20–50 μm and a porosity ofabout 90% is subjected to the so-called radiation graft polymerizationcomprising γ-ray irradiation onto the nonwoven fabric and the subsequentgraft polymerization, thereby introducing graft chains; and the graftchains thus introduced are then treated with a heated sulfuric acid tointroduce sulfonic acid groups thereinto. If the graft chains aretreated with a heated phosphoric acid, phosphate groups can beintroduced. The degree of grafting can reach 500% at its maximum, andthe capacity of the ion-exchange groups thus introduced after graftpolymerization can reach 5 meq/g at its maximum.

The base material of the ion-exchanger 48 may be a polyolefin such aspolyethylene or polypropylene, or any other organic polymer. Further,besides the form of a nonwoven fabric, the ion-exchanger may be in theform of a woven fabric, a sheet, a porous material, short fibers, etc.

When polyethylene or polypropylene is used as the base material, graftpolymerization can be effected by first irradiating radioactive rays(γ-rays or electron beam) on to the base material (pre-irradiation) tothereby generate a radical, and then reacting the radical with amonomer, whereby uniform graft chains with few impurities can beobtained. When an organic polymer other than polyolefin is used as thebase material, on the other hand, radical polymerization can be effectedby impregnating the base material with a monomer and irradiatingradioactive rays (γ-rays, electron beam or UV-rays) onto the basematerial (simultaneous irradiation). Though this method fails to provideuniform graft chains, it is applicable to a wide variety of basematerials.

By using as the ion exchanger 48 a nonwoven fabric having ananion-exchange ability or a cation-exchange ability, it becomes possiblethat pure water or ultrapure water, or a liquid such as an electrolyticsolution can freely move within the nonwoven fabric and easily arrive atthe active points in the nonwoven fabric having a catalytic activity forwater dissociation, so that many water molecules are dissociated intohydrogen ions and hydroxide ions. Further, by the movement of pure wateror ultrapure water, or a liquid such as an electrolytic solution, thehydroxide ions produced by the water dissociation can be efficientlycarried to the surface of the processing electrode 42, whereby a highelectric current can be obtained even with a low voltage applied.

When the ion exchanger 48 has only one of anion-exchange ability andcation-exchange ability, a limitation is imposed on electrolyticallyprocessible materials and, in addition, impurities are likely to formdue to the polarity. In order to solve this problem, the ion exchanger48 may have such a structure wherein anion-exchangers having ananion-exchange ability and cation-exchangers having a cation-exchangeability are concentrically disposed to constitute an integral structure.The anion exchangers and the cation exchangers may be superimposed onthe surface, to be processed, of a substrate. Alternatively, the aboveproblem can be solved by using, as the ion exchanger 48, anion-exchanger which in itself carries both of an anion-exchange groupand a cation-exchange group. Such an ion exchanger may include anamphoteric ion exchanger in which anion-exchange groups andcation-exchange groups are distributed randomly, a bipolar ion exchangerin which anion-exchange groups and cation-exchange groups are present inlayers, and a mosaic ion exchanger in which portions containinganion-exchange groups and portions containing cation-exchange groups arepresent in parallel in the thickness direction. Incidentally, it is ofcourse possible to selectively use, as the ion exchanger 48, one havingan anion-exchange ability or one having a cation-exchange abilityaccording to the material to be processed.

Further, by making the ion exchanger 48 a multi-layer structureconsisting of laminated layers of ion-exchange materials, such as anonwoven fabric, a woven fabric and a porous membrane, it is possible toincrease the total ion exchange capacity whereby formation of an oxide,for example in removal (polishing) processing of copper, can berestrained to thereby avoid the oxide adversely affecting the processingrate. In this regard, when the total ion exchange capacity of an ionexchanger is smaller than the amount of copper ions taken in the ionexchanger during removal processing, the oxide should inevitably beformed on the surface or the inside of the ion exchanger, whichadversely affects the processing rate. Thus, the formation of the oxideis governed by the ion exchange capacity of an ion exchanger, and copperions exceeding the capacity should become the oxide. The formation of anoxide can thus be effectively restrained by using, as the ion exchanger48, a multi-layer ion exchanger composed of laminated layers ofion-exchange materials which has enhanced total ion exchange capacity.In using any of the above-described ion exchangers, the formation of anoxide can also be restrained and the processing rate can be stabilizedby regenerating the ion exchanger, by means of an ion exchangerregeneration mechanism for discharging process products accumulatedwithin an ion exchanger, so as to suppress accumulation of copper ionswithin the ion exchanger.

It is also possible to make the ion exchanger 48 a multi-layer structurewith the topmost layer being composed of a soft ion exchanger (ionexchange material) such as a porous membrane or a woven fabric, or tocover the surface of the ion exchanger 48 with a water-absorbing pad.This can avoid direct contact between the ion exchanger 48 and ato-be-processed material, thereby suppressing production of fiber dustdue to friction between the ion exchanger 48 and the to-be-processedmaterial and prolonging the mechanical life of the ion exchanger 48itself.

Located above the electrode section 32, there is provided a pure waternozzle 50 as a pure water supply section, extending toward almost thecenter in the long direction of the groove 38, for supplying pure wateror ultrapure water. The pure water nozzle 50 supplies pure water orultrapure water into the groove 38 of the electrode section 32 to fillthe groove 38 with pure water or ultrapure water, and the pure water orultrapure water is discharged successively. Pure water herein refers towater having an electric conductivity of not more than 10 μS/cm, andultrapure water refers to water having an electric conductivity of notmore than 0.1 μS/cm. Instead of pure water, a liquid having an electricconductivity of not more than 500 μS/cm or any electrolytic solution maybe used. By supplying such a processing liquid during processing, theinstability factors of processing, such as process products anddissolved gases, can be removed, and processing can be effecteduniformly with good reproducibility.

With respect to the processing electrode 42 and the feeding electrode44, oxidation or dissolution thereof due to an electrolytic reaction isgenerally a problem. In view of this, it is preferred to use, as a basematerial of the feeding electrode 44, carbon, a noble metal that isrelatively inactive, a conductive oxide or a conductive ceramic, ratherthan a metal or metal compound widely used for electrodes. A noblemetal-based electrode may, for example, be one obtained by plating orcoating platinum or iridium onto a titanium electrode, and thensintering the coated electrode at a high temperature to stabilize andstrengthen the electrode. Ceramics products are generally obtained byheat-treating inorganic raw materials, and ceramics products havingvarious properties are produced from various raw materials includingoxides, carbides and nitrides of metals and nonmetals. Among them thereare ceramics having an electric conductivity. When an electrode isoxidized, the value of the electric resistance generally increases tocause an increase of applied voltage. However, by protecting the surfaceof an electrode with a non-oxidative material such as platinum or with aconductive oxide such as an iridium oxide, the decrease of electricconductivity due to oxidation of the base material of an electrode canbe prevented.

A description will now be given of an example of processing by means ofthe electrolytic processing apparatus (bevel-removal apparatus).

First, a substrate W, having e.g. a copper film 6 (see FIG. 13B) as aconductor film (to-be-processed portion) formed in the surface, isdropped between the pair of roller chucks 30, 30 to hold the substratevertically. At this time, the lowermost surface of the substrate W isclose to or in slight contact with the surface of the ion exchanger 48.

Next, a given voltage is applied from the power source 40 between theprocessing electrodes 42 and the feeding electrodes 44, while thesubstrate W is rotated. At the same time, pure water or ultrapure wateris supplied through the pure water nozzle 50 to the inside of the groove38 so as to fill the groove 38 with pure water or ultrapure water.Thereby, electrolytic processing of the conductor film (copper film 6)formed on the substrate W is effected by hydrogen ions or hydroxide ionsproduced using the ion exchanger 48. According to the above electrolyticprocessing apparatus, a large amount of hydrogen ions or hydroxide ionscan be produced by allowing pure water or ultrapure water to flow withinthe ion exchanger 48, and the large amount of such ions can be suppliedto the surface of the substrate W, whereby the electrolytic processingcan be conducted efficiently.

More specifically, by allowing pure water or ultrapure water to flowwithin the ion exchanger 48, a sufficient amount of water can besupplied to a functional group (sulfonic acid group in the case of anion exchanger carrying a strongly acidic cation-exchange group) therebyto increase the amount of dissociated water molecules, and the processproduct (including a gas) formed by the reaction between the conductorfilm (copper film 6) and hydroxide ions (or OH radicals) can be removedby the flow of water, whereby the processing efficiency can be enhanced.The flow of pure water or ultrapure water is thus necessary, and theflow of water should desirably be constant and uniform. The constancyand uniformity of the flow of water leads to constancy and uniformity inthe supply of ions and the removal of the process product, which in turnleads to constancy and uniformity in the processing.

After completion of the electrolytic processing, the power source 40 isdisconnected, the supply of pure water or ultrapure water is stopped,and then the rotation of the substrate W is stopped. Thereafter, thetransfer robot takes the processed substrate W, and then transfers thesubstrate W to the next process.

This embodiment shows the case of supplying pure water, preferablyultrapure water to the ion exchanger 48. The use of pure water orultrapure water containing no electrolyte upon electrolytic processingcan prevent impurities such as an electrolyte from adhering to andremaining on the surface of the substrate W. Further, copper ions or thelike dissolved during electrolytic processing are immediately caught bythe ion exchanger 48 through the ion-exchange reaction. This can preventthe dissolved copper ions or the like from re-precipitating on the otherportions of the substrate W, or from being oxidized to become fineparticles which contaminate the surface of the substrate W.

Ultrapure water has a high resistivity, and therefore an electriccurrent is hard to flow therethrough. A lowering of the electricresistance is made by interposing the ion exchanger 48 between theelectrodes and a substrate. Further, an electrolytic solution, when usedin combination with ultrapure water, can further lower the electricresistance and reduce the power consumption. When electrolyticprocessing is conducted by using an electrolytic solution, the portionof a workpiece that undergoes processing ranges over a slightly widerarea than the area of the processing electrode. In the case of thecombined use of ultrapure water and the ion exchanger, on the otherhand, since almost no electric current flows through ultrapure water,electric processing is effected only within the area of a workpiece thatis equal to the area of the processing electrode and the ion exchanger.

It is possible to use, instead of pure water or ultrapure water, anelectrolytic solution obtained by adding an electrolyte to pure water orultrapure water. The use of such an electrolytic solution can furtherlower the electric resistance and reduce the power consumption. Asolution of a neutral salt such as NaCl or Na₂SO₄, a solution of an acidsuch as HCl or H₂SO₄, or a solution of an alkali such as ammonia, may beused as the electrolytic solution, and these solutions may beselectively used according to the properties of the workpiece. When theelectrolytic solution is used, it is preferred to provide a slightinterspace between the substrate W and the ion exchanger 48 so that theyare not in contact with each other. To avoid contamination of thesubstrate W induced by an electrolytic solution, it is better to use adilute electrolytic solution which electric conductivity is not morethan 500 μs/cm. Therefore, the cleanliness of the processed workpiececan be increased.

Further, it is also possible to use, instead of pure water or ultrapurewater, a liquid obtained by adding a surfactant to pure water orultrapure water, and having an electric conductivity of not more than500 μS/cm, preferably not more than 50 μS/cm, more preferably not morethan 0.1 μS/cm (resistivity of not less than 10 MΩ·cm). Due to thepresence of a surfactant, the liquid can form a layer, which functionsto inhibit ion migration evenly, at the interface between the substrateW and the ion exchanger 48, thereby moderating concentration of ionexchange (metal dissolution) to enhance the flatness of the processedsurface. The surfactant concentration is desirably not more than 100ppm. When the value of the electric conductivity is too high, thecurrent efficiency is lowered and the processing rate is decreased. Theuse of the liquid having an electric conductivity of not more than 500μS/cm, preferably not more than 50 μS/cm, more preferably not more than0.1 μS/cm, can attain a desired processing rate.

According to the present invention, the processing rate can beconsiderably enhanced by interposing the ion exchanger 48 between thesubstrate W and the processing and feeding electrodes 42, 44. In thisregard, electrochemical processing using ultrapure water is effected bya chemical interaction between hydroxide ions in ultrapure water and amaterial to be processed. However, the amount of the hydroxide ionsacting as reactant in ultrapure water is as small as 10⁻⁷ mol/L undernormal temperature and pressure conditions, so that the removalprocessing efficiency can decrease due to reactions (such as an oxidefilm-forming reaction) other than the reaction for removal processing.It is therefore necessary to increase hydroxide ions in order to conductremoval processing efficiently. A method for increasing hydroxide ionsis to promote the dissociation reaction of ultrapure water by using acatalytic material, and an ion exchanger can be effectively used as sucha catalytic material. More specifically, the activation energy relatingto water-molecule dissociation reaction is lowered by the interactionbetween functional groups in an ion exchanger and water molecules,whereby the dissociation of water is promoted to thereby enhance theprocessing rate.

FIG. 5 shows an electrolytic processing apparatus (substrate processingapparatus), utilized as a bevel-removal apparatus, according to anotherembodiment of the present invention. The bevel-removal apparatus(electrolytic processing apparatus) of this embodiment employs, as theelectrode section 32 having a plurality of electrodes 36, one having asufficiently larger length than the peripheral length of the substrateW. Further, the electrode section 32 is disposed in a tilted state, e.g.by angle θ relative to a horizontal plane, whereby the substrate W isallowed to roll over the ion exchanger 48 disposed in the groove 38 andmove along the electrode section 32. The other construction is the sameas the above-described embodiment.

According to this embodiment, the substrate W spontaneously rotates byits own weight, making it possible to omit a mechanism for holding androtating a substrate, and thus simplify the construction.

According to the bevel-removal apparatuses (substrate processingapparatuses) of the above-described embodiments, electrolytic processingof a workpiece, such as a substrate, can be effected throughelectrochemical action, without causing any physical defects in theworkpiece that would impair the properties of the workpiece. Theelectrolytic processing can effectively remove (clean off) a conductivematerial formed on or adhering to a bevel portion, etc. of a substrateor process a peripheral portion of a substrate. Although theapparatuses, as shown in FIGS. 2 through 5, are accompanied with ionexchangers, the process of the present invention is achieved without anion exchanger, but by using electrolytic solution as a liquid. Theprocessing of a substrate can be effected even by solely using purewater or ultrapure water. This obviates the possibility that impuritiessuch as an electrolyte will adhere to or remain on the surface of thesubstrate, can simplify a cleaning process after the removal processing,and can remarkably reduce a load upon waste liquid disposal.

FIG. 6 is a schematic sectional view of an electrolytic processingapparatus 511 as a substrate processing apparatus according to stillanother embodiment of the present invention. The electrolytic processingapparatus 511 comprises an electrode holding section 512 for holding aprocessing electrode 518, an electrode-rotating shaft 513 secured to theelectrode holding section 512, a substrate holding section 514, providedbelow the electrode holding section 512, for sucking and holding asubstrate W as a workpiece (e.g. a wafer having a copper film 6 as shownin FIG. 13B), and a substrate-rotating shaft 515 secured to thesubstrate holding section 514. According to this embodiment, thesubstrate W functions as a feeding electrode, as will be describedbelow. The electrolytic processing apparatus 511 also includes a powersource 523 for applying a voltage between the processing electrode 518and the substrate W. The electrode holding section 512 moves relative tothe substrate holding section 514, as will be described later.

The electrolytic processing apparatus 511 is also provided with a hollowmotor 541 as a substrate-rotating means for rotating the substrateholding section 514 via the substrate-rotating shaft 515 (rotation aboutthe central axis of the substrate-rotating shaft 515 (rotation L)); ahollow motor 542 as an electrode-rotating means for eccentricallyrotating the electrode holding section 512 about a vertical axis via theelectrode-rotating shaft 513 (rotation U); a pivot arm 543, a pivotshaft 544 and a pivot motor 545, as an electrode-pivoting means forpivoting the electrode holding section 512 toward a position right abovethe substrate holding section 514, or pivoting the electrode holdingsection 512 horizontally from the position right above the substrateholding section 514; a ball screw 546 and a vertical movement motor 547,as a vertical movement means for raising the electrode holding section512 away from the substrate holding section 514, or lowering it close tothe substrate holding section 514; and a processing liquid supply means(not shown) as a fluid supply means for supplying a processing liquid502 as a fluid. The pivot arm 543 is driven by the pivot motor 545, andpivots the electrode holding section 512. The ball screw 546 is drivenby the vertical movement motor 547, and raises and lowers the pivotshaft 544, the pivot arm 543 and the electrode holding section 512.

The electrode holding section 512 has a substantially discoidal shape,and is disposed horizontally. A circumferential wall 516 is formed atthe periphery of the lower surface 512 b of the electrode holdingsection 512. A concave section 517 is formed by the circumferential wall516 in the lower surface 512 b of the electrode holding section 512. Theprocessing electrode 518 in a discoidal shape is mounted horizontally tothe end of the circumferential wall 516. A through-hole 519 is formed inthe center of the electrode holding section 512. A number ofthrough-holes 519 are formed in the processing electrode 518 forsupplying the processing liquid 502 to the substrate W. The processingelectrode 518 is designed to have a radius larger than the radius of thesubstrate W.

The electrode-rotating shaft 513 in a hollow cylindrical shape ismounted vertically on the upper surface 512 a of the electrode holdingsection 512. A hollow passage 520 is formed in the electrode-rotatingshaft 513, and the hollow passage 520 communicates with the through-hole519 of the electrode holding section 512. The hollow motor 542 iscoupled to the upper end 513 a of the electrode-rotating shaft 513, andthe hollow portion 542 c of the hollow motor 542 communicates with thehollow passage 520. A hollow portion 548 is formed at the connection ofthe pivot arm 543 with the hollow motor 542, and the hollow portion 548communicates with the hollow portion 542 c. The hollow motor 542 isprovided on the lower surface 543 a of the pivot arm 543 in the vicinityof the free end 543 c of the pivot arm 543.

An electric wire 524, which is connected to the upper surface 518 a ofthe processing electrode 518, passes through the concave section 517,the through-hole 519, the hollow passage 520, the hollow portion 542 cand the hollow portion 548, through a slip ring 526 provided on theupper surface 543 b of the pivot arm 543, and then through a hollowportion 539 formed in the pivot arm 543 and in the pivot shaft 544, andconnects with the power source 523. A processing liquid supply inlet 528as a fluid supply section is formed in the electrode-rotating shaft 513,and a processing liquid supply means (not shown) supplies the processingliquid 502 to the supply inlet 528 of the electrode-rotating shaft 513.

The substrate holding section 514 has a discoidal shape, and is disposedhorizontally. The substrate holding section 514 sucks and holds thesubstrate W on the upper surface 514 a that the electrodeposited Cusurface faces upwardly. A through-hole 521 is formed in the center ofthe substrate holding portion 514.

The substrate-rotating shaft 515 in a hollow cylindrical shape ismounted vertically on the lower surface 514 b of the substrate holdingsection 514. A hollow passage 522 is formed in the substrate-rotatingshaft 515, and the hollow passage 522 communicates with the through-hole521 of the substrate holding section 514. The hollow motor 541 iscoupled to the lower end 515 b of the substrate-rotating shaft 515. Thehollow portion 541 c of the hollow motor 541 communicates with thehollow passage 522.

An electric wire 525, which is connected to the lower surface WB, i.e.the copper layer 6 (see FIG. 13B) of the substrate W, passes through thethrough-hole 521, the hollow passage 522 and the hollow portion 541 c,and then through a slip ring 527 provided on the lower surface 541 b ofthe hollow motor 541, and connects with the power source 523. Theelectrolytic processing apparatus 511 of the present embodiment is ofthe direct feeding type which feeds electricity directly to thesubstrate W. The substrate W is disposed in parallel with the processingelectrode 518.

As shown in FIG. 7A, the substrate W, which is to be held by suction onthe upper surface 514 a (see FIG. 6) of the substrate holding section514, may be of the shape of a thin disc in which a seed layer 7 (e.g.copper seed layer) as a film, or as a first film is formed all over theupper surface WA, and a copper film (plated layer) 6 as a film, or as asecond film is formed in the effective device portion 533 of thesubstrate, i.e. the other portion of the substrate W other than theperipheral portion 532. Typically, the copper film 6 is formed morethickly than the seed layer 7. Further, the substrate W has such a filmformation that there is a step between the peripheral portion 532 andthe effective device portion 533. Incidentally, regarding FIGS. 7A and7B, the seed layer 7 and the copper film 6 are drawn more thickly thanthe real ones.

The operation of the electrolytic processing apparatus 511 of thisembodiment will now be described by referring to FIG. 6.

The substrate W is placed on the upper surface 514 a of the substrateholding section 514 and held by suction thereon. The pivot motor 545pivots, via the pivot shaft 544, the pivot arm 543 about the pivot shaft544, whereby the electrode holding section 512 is pivoted horizontallyby the pivot arm 543 and reaches a position right above the substrateholding section 514. Thereafter, the vertical movement motor 547 rotatesthe ball screw 546 and lowers the pivot shaft 544, and the pivot shaft544 lowers, via the pivot arm 543, the electrode holding section 512toward the substrate holding section 514, so that the upper surface WAof the substrate W comes close to the lower surface 518 b of theprocessing electrode 518.

The processing liquid 502 is supplied by a processing liquid supplymeans (not shown) to the processing liquid supply inlet 528. Theprocessing liquid 502 passes through the hollow passage 520, thethrough-hole 519, the concave 517 and the through-holes 529, and issupplied to the entire upper surface WA of the substrate W from theentire surface 518 b, facing the substrate W, of the processingelectrode 518. Thereafter, a voltage is applied from a power source 523between the processing electrode 518 and the substrate W. In thisembodiment, the voltage is applied so that the processing electrode 518side becomes a cathode, and the substrate W side becomes an anode. Then,the electrode holding portion 512 is rotated eccentrically (rotation U)at a predetermined angular rate by the hollow motor 542 via theelectrode-rotating shaft 513, and the substrate holding section 514 isrotated (rotation L) at a predetermined angular rate by the hollow motor541 via the substrate-rotating shaft 515. It is preferable that thehollow motors 541 and 542 respectively eccentrically rotate, and therebyrotate the electrode holding portion 512 and the substrate W in such amanner that the processing electrode 518 can process the entire uppersurface WA of the substrate W periodically, and removal processing ofthe seed layer 7 and the copper film 6 can be effected at a uniformprocessing rate. Incidentally, since the processing electrode 518rotates eccentrically and the substrate W rotates, the processingelectrode 518 moves relative to the substrate W.

Next, the vertical movement motor 547 further rotates the ball screw 546to further lower the electrode holding section 512 to a position atwhich the processing electrode 518 and the upper surface WA of thesubstrate W are opposed to each other at a slight distance. Therefore,treatment of the substrate W, i.e. electrolytic processing of the copperfilm 6 and the seed layer 7, is carried out.

Since the lower surface 518 b of the processing electrode 518 and theupper surface WA of the substrate W, as a workpiece or as a feedingelectrode, are thus opposed and close to each other, when water, purewater or ultrapure water, for example, is used as the processing liquid502, water molecules dissociate into hydroxide ions (OH⁻) and hydrogenions (H⁺). By the flow of the liquid and by the electric field betweenthe substrate W and the processing electrode 518, the density of thehydroxide ions (OH⁻), produced by the dissociation of water molecules,increases in the vicinity of the upper surface WA of the substrate W,whereby a reaction between the atoms of the copper film 6 and thehydroxide ions (OH⁻) and a reaction between the atoms of the seed layer7 and the hydroxide ions (OH⁻) can occur. The reaction products of thesereactions are removed from the substrate W. Removal processing of thecopper film 6 and the seed layer 7 is thus effected.

The processing of the substrate W is terminated at the time when theremoval of the seed layer 7 in the peripheral portion 532 is completed,as shown in FIG. 7B. In FIG. 7B, the broken lines denote the surface ofthe substrate before the processing. By the processing, the film in theupper surface WA of the substrate W is removed by an even thickness tover the entire upper surface WA simultaneously. The seed layer 7 in theperipheral portion 532 is thus completely removed, whereas the copperfilm 6 in the effective device portion 533 still remains. Selectivepeeling or complete removal of the seed layer 7 in the peripheralportion 532 can thus be achieved.

According to this embodiment, the end portion of the complete filmremoval region in the substrate surface WA naturally corresponds to theboundary between the peripheral portion 532 and the effective deviceportion 533, meaning that the complete film removal width isautomatically determined. Further, since the so-called electrolyticbevel processing can be performed simultaneously with processing of theeffective device portion 533, the number of process steps can bedecreased. The electrolytic processing apparatus of this embodiment canthus simplify the film removal step for peeling or completely removingthe seed layer 7 in the peripheral portion 532 and perform processing ofthe peripheral portion 532 without the necessity of control of theprocessing region.

Next, the vertical movement motor 547 reverses the rotation of the ballscrew 546 to raise the electrode holding section 512, and the rotation(rotation U) of the electrode holding section 512 by the hollow motor542 and the rotation (rotation L) of the substrate holding section 514by the hollow motor 541 are terminated. The voltage application by thepower source 523 is also terminated. The pivot motor 545 pivots thepivot arm 543 via the pivot shaft 544, thereby pivoting horizontally theelectrode holding portion 512 away from the position right above thesubstrate holding portion 514. The substrate W is then taken out of thesubstrate holding section 514.

It is desirable to use as the processing liquid 502 a liquid obtained byadding an additive, such as a surfactant, to water, pure water orultrapure water, and having an electric conductivity of not more than500 μS/cm, preferably not more than 50 μS/cm, more preferably not morethan 10 μS/cm, especially preferably not more than 0.1 μS/cm. The use ofsuch a liquid makes it possible to carry out clean processing, withoutleaving impurities, or dipolar molecules having a strong adhesion to theprocessed surface, on the substrate surface WA and reduce roughness ofthe processed surface, whereby a cleaning step for cleaning thesubstrate W after the electrolytic processing can be simplified.

An aqueous solution of a neutral salt such as NaCl or Na₂SO₄, an acidsuch as HCl or H₂SO₄, or an alkali such as ammonia may also be used asthe processing liquid 502, and may be properly selected according to theproperties of a workpiece (substrate).

FIG. 8 is a schematic sectional view of an electrolytic processingapparatus 111 as a substrate processing apparatus according to stillanother embodiment of the present invention. Compared to theelectrolytic processing apparatus 511 shown in FIG. 6, the electrolyticprocessing apparatus 111 of this embodiment differs in that an ionexchanger 135 is mounted on the lower surface 118 b of a processingelectrode 118 such that it covers the entire lower surface 118 b, theother construction of the electrolytic processing apparatus 111 beingthe same as the electrolytic processing apparatus 511. The electrolyticprocessing apparatus 111 of this embodiment is also of the directfeeding type which feeds electricity directly to the substrate W. Aswith the electrolytic processing apparatus 511 of FIG. 6, a processingliquid 102 is supplied from a processing liquid supply inlet 128 as afluid supply section, a voltage is applied from a power source 123between the processing electrode 118 and the substrate W, and thesubstrate W shown in FIG. 7A can be processed.

In FIG. 8, the description of a hollow motor which is connected to anelectrode-rotating shaft 113 and rotates an electrode holding section112, a pivot arm, a pivot shaft, a pivot motor, a slip ring mounted onthe pivot arm, a hollow motor which is connected to a substrate-rotatingshaft 115 and rotates a substrate holding section 114, a slip ringmounted on the hollow motor, a ball screw and a vertical movement motoris omitted.

According to the electrolytic processing apparatus 111 of thisembodiment which is provided with the ion exchanger 135, in carrying outprocessing of the substrate W, a vertical movement means (not shown)lowers the electrode holding section 112 until the ion exchanger 135comes into contact with the upper surface WA of the substrate W.

Due to the provision of the ion exchanger 135, the operation of theelectrolytic processing apparatus 111 differs from that of theelectrolytic processing apparatus 511 shown in FIG. 6, as explainedbelow.

According to the electrolytic processing apparatus 111 of thisembodiment, when water, pure water or ultrapure water, for example, issupplied as the processing liquid 102, the processing liquid 102supplied flows between the substrate W and the ion exchanger 135. Theion exchanger 135 then effectively promotes the dissociation of theprocessing liquid 102 to produce plenty of hydroxide ions and hydrogenions. By the flow of the processing liquid 102 and by the electric fieldbetween the substrate W and the processing electrode 118, the density ofhydroxide ions increases in the vicinity of the upper surface WA of thesubstrate W, whereby reaction between the atoms of the copper film 6 andhydroxide ions and reaction between the atoms of the seed layer 7 andhydroxide ions can occur. The use of the ion exchanger 135, which canproduce plenty of hydroxide ions, can further enhance the density ofhydroxide ions in the vicinity of the substrate upper surface WA,enabling an efficient processing to remove a predetermined eventhickness of film simultaneously from the seed layer 7 and from thecopper film 6 over the entire upper surface WA of the substrate W andthereby shortening the processing time. The predetermined thicknessshould at least be the thickness of the seed layer 7 in the peripheralportion 532 of the substrate.

The ion exchanger 135 may either be of a single layer structure or of amulti-layer laminated structure. Some of the processing products(hydroxides and ions) of the electrolytic reactions accumulate on thesurface or in the inside of the ion exchanger, and the amount of theaccumulation depends upon the ion exchange capacity of the ionexchanger. When the amount of the accumulated processing productsexceeds the ion exchange capacity of the ion exchanger, the accumulatedproducts can change their forms, which can affect the processing rateand its distribution. Accordingly, it is necessary not to accumulate theprocessing products in the ion exchanger in an amount exceeding the ionexchange capacity, or to remove the accumulated products from the ionexchanger. A multi-layer laminated ion exchanger generally has anenhanced ion exchange capacity.

FIG. 9 is a schematic sectional view of an electrolytic processingapparatus 201 as a substrate processing apparatus according to stillanother embodiment of the present invention.

As with the electrolytic processing apparatus 111 shown in FIG. 8, theelectrolytic processing apparatus 201 of this embodiment includes anelectrode holding section 212, a substrate holding section 214, aprocessing electrode 218 and an ion exchanger 235. The ion exchanger 235is mounted on the lower surface 218 b of the processing electrode 218such that the ion exchanger 235 covers the entire lower surface 218 b. Aconcave section 217 is formed by a circumferential wall 216 in the lowersurface 212 b of the electrode holding section 212. A through-hole 219is formed in the center of the electrode holding section 212.

Further, a number of through-holes 229 are formed in the processingelectrode 218 for supplying a processing liquid 202 as a fluid to thesubstrate W. An electrode-rotating shaft 213 in a hollow cylindricalshape is mounted vertically on the upper surface 212A of the electrodeholding section 212. A hollow passage 220 is formed in theelectrode-rotating shaft 213, and the hollow passage 220 communicateswith the through-hole 219 of the electrode holding section 212. Aprocessing liquid supply inlet 228 is formed in the electrode-rotatingshaft 213, and the processing liquid supply inlet 228 communicates withthe hollow passage 220. The processing liquid 202 supplied to theprocessing liquid supply inlet 228 passes through the hollow passage220, the through-hole 219, the concave section 217 and the through-holes229, and is supplied from the entire surface 218 b, facing the substrateW, of the processing electrode 218. According to the electrolyticprocessing apparatus 201 of this embodiment, as with the electrolyticprocessing apparatus 111 shown in FIG. 8, the substrate W shown in FIG.7A can be processed.

In FIG. 9, the description of a hollow motor which is connected to theelectrode-rotating shaft 213 and rotates the electrode holding section212, a pivot arm, a pivot shaft, a pivot motor, a slip ring mounted onthe pivot arm, a motor which is connected to a substrate-rotating shaft215 and rotates the substrate holding section 214, a ball screw and avertical movement motor, is omitted.

The electrolytic processing apparatus 201 of this embodiment has thesame construction as the electrolytic processing apparatus 111 shown inFIG. 8, except for the following respects.

According to the electrolytic processing apparatus 201 of thisembodiment, a hollow passage is not formed in the substrate-rotatingshaft 215, that is, the substrate-rotating shaft 215 comprises a solidshaft. The motor (not shown in FIG. 9), connected to thesubstrate-rotating shaft 215, for rotating the substrate holding section214 does not have a hollow portion, and a slip ring is not mounted onthe motor. A hollow portion for passing therethrough an electric wire isnot formed in the pivot arm and in the pivot shaft (both not shown inFIG. 9).

In the case of the electrolytic processing apparatus 111 shown in FIG.8, as described above, the processing electrode 118 is mounted on theelectrode holding section 112, and the substrate W, held by suction onthe substrate holding section 114, functions as a feeding electrode.According to the electrolytic processing apparatus 201 of thisembodiment, on the other hand, feeding electrode 236, together with theprocessing electrode 218, is mounted on the electrode holding section212, and an insulator section 237 is provided between the processingelectrode 218 and the feeding electrode 236. Thus, the electrolyticprocessing apparatus 201 of this embodiment is of the so-called one sidefeeding type.

An electric wire 225 connected to the feeding electrode 236, togetherwith an electric wire 224 connected to the processing electrode 218,passes through the concave section 217, the through-hole 219, the hollowpassage 220, a hollow portion (not shown) formed in a hollow motor (notsown) for rotating the electrode holding section 212 and a hollowportion (not shown) formed in the pivot arm (not shown), and furtherthrough a slip ring (not shown) provided on the upper surface of thepivot arm, and connects with a power source 223.

As shown in FIG. 10, the processing electrode 218 may be composed ofthree fan-shaped processing electrode elements 218 c to 218 e, and thefeeding electrode may be composed of three fan-shaped feeding electrodeelements 236 c to 236 e; and the processing electrode elements 218 c to218 e and the feeding electrode elements 236 c to 236 e may be disposedalternately in the circumferential direction. The insulator section 237may include a portion 237 a disposed in the center of the electrodeholding section 212 and a portion 237 b disposed radially between theprocessing electrode elements 218 c to 218 e and the feeding electrodeelements 236 c to 236 e. Through-holes 229, in which the processingliquid 202 flows, may be formed in the processing electrode elements 218c to 218 e and the feeding electrode elements 236 c to 236 e. In FIG.10, only the through-holes 229 formed in the processing electrodeelement 218 c are shown. Though not shown, through-holes 229 arelikewise formed in the other processing electrode elements 218 d and 218e and in the feeding electrode elements 236 c to 236 e.

As shown in FIGS. 9 and 10, electric wires are connected to theprocessing electrode elements 218 c to 218 e and to the feedingelectrode elements 236 c to 236 e. Three electric wires (only one isshown) for the processing electrode elements 218 c to 218 e areassembled into one electric wire 224, and three electric wires (only oneis shown) for the feeding electrode elements 236 c to 236 e areassembled into one electric wire 225; and the electric wires 224, 225are connected, via the concave section 217, the through-hole 219, thehollow passage 220 and a slip ring (not shown), to the power source 236.

The electrolytic processing apparatus 201 of this embodiment operates inalmost the same manner as the electrolytic processing apparatus 111shown in FIG. 8, except that the substrate W held on the substrateholding section 214 does not function as a feeding electrode.

The electrolytic processing apparatus 201 of this embodiment, owing tothe provision of the ion exchanger 235, can perform an efficientelectrolytic processing. Further, since the substrate W is not utilizedas a feeding electrode, not only a conductive substrate W, but also anon-conductive substrate W on which a conductive film is formed, can beprocessed.

Incidentally, in the above-described electrolytic processing apparatus511 shown in FIG. 6, instead of mounting the disc-shaped processingelectrode 518 on the electrode holding section 512, it is possible tomount such a disc-shaped electrode (processing and feeding electrodes)as shown in FIG. 10 in which processing electrode elements and feedingelectrode elements are disposed alternately in the circumferentialdirection, thereby making the electrolytic processing apparatus a oneside feeding type instead of the direct feeding type.

In this case, the electric wire 524 connected to each processingelectrode element and the electric wire 525 connected to each feedingelectrode element together pass through the concave section 517, thethrough-hole 519, the hollow passage 520, the hollow portion 542 c andthe hollow portion 548, and further through the slip ring 526 providedon the upper surface 543 b of the pivot arm 543, and connect with thepower source 523. Thus, the electric wire 525 is not connected to thecopper film 6 (see FIG. 7A and FIG. 13B) of the substrate W.

FIG. 11 is a schematic sectional view of a chemical etching apparatus311 as a substrate processing apparatus according to an embodiment ofthe present invention. The chemical etching apparatus 311 of thisembodiment is a chemical etching apparatus, which uses an etching liquid302 instead of a processing liquid, and, as compared to the electrolyticprocessing apparatus 511 shown in FIG. 6, has the below-describedconstructional differences. As with the electrolytic processingapparatus 511 shown in FIG. 6, the substrate W shown in FIG. 7A can beetch-processed by this chemical etching apparatus 311.

The chemical etching apparatus 311 includes a processing head holdingsection 312 which holds a disc-shaped processing head 318. A processinghead-rotating shaft 313 for rotating the processing head 318 is securedto the processing head holding section 312. The processing head holdingsection 312, the processing head-rotating shaft 313 and the processinghead 318 respectively have the same shapes as the electrode holdingsection 512, the electro-rotating shaft 513 and the processing electrode518 shown in FIG. 6. As with the electrode-rotating shaft 513 shown inFIG. 6, the processing head-rotating shaft 313 rotates the processinghead 318. A number of through-holes 329 are formed in the processinghead 318 for passing therethrough the etching liquid 302 and supplyingthe etching liquid 302 to the entire upper surface WA of the substrateW.

The chemical etching apparatus 311 is not provided with a power source,and a voltage is not applied between the processing head 318 and thesubstrate W. Accordingly, the chemical etching apparatus 311 does nothave an electric wire and is not provided with a slip ring. Further, ahollow passage for passing therethrough an electric wire is not formedin a substrate-rotating shaft 315 which is secured to a substrateholding section 314.

The chemical etching apparatus 311 also includes a motor 341 as asubstrate-rotating means for rotating the substrate holding section 314secured to a substrate-rotating shaft 315 via the substrate-rotatingshaft 315 (rotation about the central axis of the substrate-rotatingshaft 315 (rotation L)); a motor 342 as a processing head-rotating meansfor eccentrically rotating the processing head holding section 312secured to the processing head-rotating shaft 313 about a vertical axis(rotation U); a pivot arm 343, a pivot shaft 344 and a pivot motor 345,as a processing head-pivoting means for pivoting the processing headholding section 312 toward a position right above the substrate holdingsection 314, or pivoting the processing head holding section 312horizontally from the position right above the substrate holding section314; a ball screw 346 and a vertical movement motor 347, as a verticalmovement means for raising the processing head holding section 312 awayfrom the substrate holding section 314, or lowering it close to thesubstrate holding section 314; and an etching liquid supply means (notshown) as a fluid supply means for supplying an etching liquid 302 as afluid. The pivot arm 343 is driven by the pivot motor 345, and pivotsthe processing head holding section 312. The ball screw 346 is driven bythe vertical movement motor 347, and raises and lowers the pivot shaft344, the pivot arm 343 and the processing head holding section 312.

The operation of the chemical etching apparatus 311 of this embodimentdiffers from that the electrolytic processing apparatus 511 shown inFIG. 6 in the following respects. The etching liquid 302 is used insteadof the processing liquid 502, and a voltage is not applied between theprocessing head 318 and the substrate W.

The chemical etching apparatus 311 of the present embodiment can performetch-processing of e.g. a copper-plated substrate as shown in FIG. 7A,having a seed layer (copper seed layer) 7 and a copper film (platedlayer) 6. As the etching liquid 302, an oxidative acid (e.g. HNO₃solution) which can dissolve copper, a combination of an oxidizing agentand an acid (e.g. H₂O₂ and HF solution), an alkali liquid (e.g. conc.NH₄OH), an organic acid solution, an organic alkali solution, etc. maybe used.

According to this embodiment, the seed layer 7 and the copper film 6 ofthe substrate W can be etched by the etching liquid 302 at a uniformetch-processing rate. The etch-processing of the substrate W isterminated at the time when the removal of the seed layer 7 in theperipheral portion 532 is completed, as shown in FIG. 7B. By theetch-processing, the film in the upper surface WA of the substrate W isremoved by an even thickness t over the entire upper surface WAsimultaneously. The seed layer 7 in the peripheral portion 532 is thuscompletely removed, whereas the copper film 6 in the effective deviceportion 533 still remains.

The chemical etching apparatus 311 of this embodiment can thus simplifyremoval of the seed layer 7 in the peripheral portion 532 and securelyremove the seed layer 7. Since the end portion of the complete filmremoval region in the substrate surface WA naturally corresponds to theboundary between the peripheral portion 532 and the effective deviceportion 533, the complete film removal width is automaticallydetermined. Further, since the so-called bevel etching can be performedsimultaneously with processing of the effective device portion 533, thenumber of process steps can be decreased.

The above-described apparatuses shown in FIGS. 6 through 11 are of theso-called “face-up type”, according to which the substrate is held bysuction on the substrate holding section disposed at a lower position,the processing electrode or the processing head is held by the electrodeholding section or by the processing head holding section disposed at anupper position, and the upper surface of the substrate is processed withthe lower surface of the processing electrode or of the processing head.It is however possible to employ the so-called “face-down type”according to which the substrate is held by suction by a substrateholding section disposed at an upper position, a processing electrode ora processing head is held by an electrode holding section or by aprocessing head holding section disposed at a lower position, and thelower surface of the substrate is processed with the upper surface ofthe processing electrode or of the processing head.

Further, according to the above-described apparatuses, the electrodeholding section or the processing head holding section is allowed torotate eccentrically (rotation U) about a vertical axis. But to make arelative movement between the processing section and the substrate, itis possible to design the apparatuses so that the electrode holdingsection or the processing head holding section is allowed to make ascroll (orbital) movement or a reciprocating movement. By the scrollmovement or reciprocating movement, the processing electrode or theprocessing head may process the entirety of the opposed surface of thesubstrate in a periodical manner.

A description will now be given of an electrolytic processing method(substrate processing method) according to an embodiment of the presentinvention by referring to FIGS. 7A, 7B and FIG. 8.

Taking a copper-plated substrate as an example, the seed layer 7 isfirst formed over the entire substrate surface WA. Next, the copper film6 is formed in the effective device portion 533 of the substrate surfaceWA. Accordingly, the film thus formed has a step between the peripheralportion 532 and the effective device portion 533 of the substratesurface WA. The processing electrode 118 is moved close to the substrateW so that the ion exchanger 135 gets positioned between the substrate Wand the processing electrode 118. The substrate W, the ion exchanger 135and the processing electrode 118 may be positioned such that thesubstrate W is in contact with the ion exchanger 135. The processingliquid 102 is supplied between the substrate W and the ion exchanger135. The processing liquid 102 may be supplied so that it can spreadover the entire interspace or interface between the substrate W and theion exchanger 135. Next, a voltage is applied from the power source 123to between the processing electrode 118 and the substrate W. Upon thevoltage application, the substrate W functions as a feeding electrode. Afeeding electrode is thus provided. The processing electrode 118 is thenmoved relative to the substrate W. The ion exchanger 135 may movetogether with the processing electrode 118. Further, the processingelectrode 118 and the ion exchanger 135 may be moved over the entiresurface WA being processed in a periodical manner.

Processing of the substrate W is terminated at the time when the seedlayer 7 in the peripheral portion 532 is completely removed. By theprocessing, the film in the upper surface WA of the substrate W isremoved by an even thickness t over the entire upper surface WAsimultaneously.

Water molecules dissociate into hydroxide ions (OH⁻) and hydrogen ions(H⁺). By the flow of the processing liquid 102 and by the electric fieldbetween the substrate W and the processing electrode 118, the density ofthe hydroxide ions, produced by the dissociation of water molecules,increases in the vicinity of the upper surface WA of the substrate W,whereby reaction between the atoms of the copper film 6 and thehydroxide ions and reaction between the atoms of the seed layer 7 andthe hydroxide ions can occur. The reaction products of these reactionsdissolve in the processing liquid 102 and, by the flow of the processingliquid 102 along the to-be-placed surface of the substrate W, areremoved from the substrate W. Removal processing of the copper film 6and the seed layer 7 is thus effected.

It is desirable to use as the processing liquid a liquid obtained byadding an additive, such as a surfactant, to water, pure water orultrapure water, and having an electric conductivity of not more than500 μS/cm, preferably not more than 50 μS/cm, more preferably not morethan 10 μS/cm, especially preferably not more than 0.1 μS/cm. The use ofsuch a liquid makes it possible to carry out clean processing, withoutleaving impurities on the substrate surface WA, whereby a cleaning stepfor cleaning the substrate W after the electrolytic processing can besimplified.

Next, a description will be given of an electrolytic processing method(substrate processing method) according to another embodiment of thepresent invention by referring to FIGS. 7A, 7B and FIG. 9.

Taking a copper-plated substrate as an example, the seed layer 7 isfirst formed over the entire substrate surface WA. Next, the copper film6 is formed in the effective device portion 533 of the substrate surfaceWA. Accordingly, the film thus formed has a step between the peripheralportion 532 and the effective device portion 533 of the substratesurface WA. The processing electrode 218 and the feeding electrode 236are moved close to the substrate W so that the ion exchanger 235 getspositioned between the substrate W and the processing electrode 218, andbetween the substrate W and the feeding electrode 236. The processingliquid 202 as a fluid is supplied between the substrate W and the ionexchanger 235. A voltage is applied from the power source 223 to betweenthe processing electrode 218 and the feeding electrode 236. Theprocessing electrode 218, the feeding electrode 236 and the ionexchanger 235 are then moved relative to the substrate W. The processingelectrode 218, the feeding electrode 236 and the ion exchanger 235 maybe moved over the entire surface WA being processed in a periodicalmanner.

Processing of the substrate W is terminated at the time when the seedlayer 7 in the peripheral portion 532 is completely removed. By theprocessing, the film in the upper surface WA of the substrate W isremoved by an even thickness t over the entire upper surface WAsimultaneously.

With the provision of the ion exchanger 235 between the substrate W andthe processing electrode 218, and between the substrate W and thefeeding device 236, the electric processing method of this embodimentcan carry out an efficient electrolytic processing. Further, since thesubstrate W is not utilized as a feeding electrode, not only aconductive substrate W but also a non-conductive substrate W can beprocessed.

A substrate processing system 401, which is provided with theelectrolytic processing apparatus (substrate processing apparatus) 111shown in FIG. 8, will now be described by referring to FIG. 12. Thoughany of the electrolytic processing apparatus 511 shown in FIG. 6, theelectrolytic processing apparatus 201 shown in FIG. 9 and the chemicaletching apparatus 311 shown in FIG. 11 may be adopted, a case ofadopting the electrolytic processing apparatus 111 is herein taken as anexample and will be described by also referring to FIG. 8 as necessary.As shown in FIG. 12, the substrate processing system 401 includes a pairof loading/unloading sections 430 as a substrate carry-in-and-outsection for carrying in and out a substrate W (see FIG. 7A and FIG.13B), a reversing machine 432 for reversing the substrate W, and theelectrolytic processing apparatus 111, which are disposed in series. Atransfer robot 438 a as a transfer device is provided which can moveparallel to these apparatuses for transporting and transferring thesubstrate W therebetween.

The substrate processing system 401 is also provided with a controlsection 442 for monitoring a voltage applied between the processingelectrode 118 (see FIG. 8) and the substrate (feeding electrode) W (seeFIG. 8) upon electrolytic processing in the electrolytic processingapparatus 111, or an electric current flowing therebetween, andcontrolling at least one of the voltage and the electric currentindependently. The substrate processing system 401, with the provisionof the electrolytic processing apparatus 111, can perform in a simplemanner an effective removal processing of a substrate W, in which a filmis formed in the substrate surface WA such that the film has a stepbetween the peripheral portion 532 (see FIG. 7A) and the effectivedevice portion 533 (see FIG. 7A) of the substrate W, thereby removingthe film by a predetermined thickness over the entire surface WAsimultaneously, and securely removing the film in the peripheral portion532 while leaving the film in the effective device portion 533.

When the material of a substrate as a workpiece is copper, molybdenum,iron, tungsten or the like, electrolytic processing action occurs on thecathode side. Therefore, a voltage is applied so that the processingelectrode side becomes a cathode and the substrate or feeding electrodeside becomes an anode. Conversely, when the material of a substrate isaluminum, silicon or the like, electrolytic processing action occurs onthe anode side. Therefore, a voltage is applied so that the processingelectrode side becomes an anode and the substrate or feeding electrodeside becomes a cathode.

As described hereinabove, the present electrolytic processingapparatuses shown in FIGS. 6 through 10 and the present chemical etchingapparatus shown in FIG. 11 both can perform in a simple manner aneffective removal processing of a substrate, in which a film is formedin the surface such that the film has a step between the peripheralportion and the effective device portion of the substrate, therebyremoving the film by a predetermined thickness over the entire substratesurface simultaneously, and securely removing the film in the peripheralportion and leaving the film in the effective device portion.

The present application is available for PCT/JP02/01545, filed on Feb.21, 2002, the entire disclosure of which is hereby incorporated byreference.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

INDUSTRIAL APPLICABILITY

This invention relates to a substrate processing apparatus and methodwhich can be utilized as a bevel-removal apparatus for processing aconductive material or removing impurities adhering to a peripheralportion (bevel portion or edge portion) of a substrate, such as asemiconductor wafer, or which can be used for carrying out a processingto remove a film formed on the surface of a substrate.

1. A substrate processing apparatus comprising: an electrode sectionhaving a plurality of electrodes which are laminated with insulatorsbeing interposed therebetween, and having a holding portion shaped andarranged so as to be opposed to only a peripheral portion of a substrateso as to remove conductive material from only the peripheral portion ofthe substrate; a liquid supply section for supplying a liquid to theholding portion of the electrode section; and a power source forapplying a voltage to the electrodes of the electrode section so thatthe electrodes alternately have different polarities.
 2. The substrateprocessing apparatus according to claim 1, further comprising an ionexchanger disposed in the holding portion of the electrode section. 3.The substrate processing apparatus according to claim 2, wherein saidion exchanger has water-absorbing properties.
 4. The substrateprocessing apparatus according to claim 2, wherein said ion exchangerhas one or both of an anion-exchange ability and a cation-exchangeability.
 5. The substrate processing apparatus according to claim 2,wherein said electrode section is arranged so as to be tilted relativeto a horizontal plane, and shaped and arranged so that the substrate canroll on edge over the ion exchanger disposed in the holding portion ofthe electrode section and can move along the electrode section.
 6. Thesubstrate processing apparatus according to claim 1, wherein said liquidis pure water, a liquid having an electric conductivity of not more than500 μS/cm, or an electrolysis solution.
 7. The substrate processingapparatus according to claim 6, wherein said pure water is ultrapurewater.
 8. The substrate processing apparatus according to claim 1,wherein the peripheral portion of the substrate is a bevel portion ofthe substrate.
 9. The substrate processing apparatus according to claim8, wherein the bevel portion of the substrate is a region several mmwide extending inward from a peripheral end of the substrate.
 10. Thesubstrate processing apparatus according to claim 1, wherein theelectrode section is shaped and arranged to face an end of thesubstrate.
 11. The substrate processing apparatus according to claim 10,wherein the electrode section has a groove conforming to a sectionalconfiguration of the peripheral portion of the substrate.
 12. Thesubstrate processing apparatus according to claim 11, wherein the grooveis shaped to extend in an arc conforming with a shape of the peripheralportion of the substrate.
 13. The substrate processing apparatusaccording to claim 10, wherein the electrode portion comprises a flatplate.
 14. The substrate processing apparatus according to claim 1,wherein the holding portion has a U-shaped groove for receiving theperipheral portion of the substrate during application of the voltage tothe electrodes of the electrode section by the power source.
 15. Thesubstrate processing apparatus according to claim 14, further comprisingan ion exchanger on a surface of the U-shaped groove of the holdingportion.
 16. A substrate processing method comprising: arranging only aperipheral portion of a substrate to oppose a holding portion of anelectrode section having a plurality of electrodes, the electrodes beinglaminated with insulators being interposed therebetween; supplying aliquid to the holding portion of the electrode section; and applying avoltage to the electrodes of the electrode section so that theelectrodes alternately have different polarities, thereby removingconductive material from only the peripheral portion of the substrate.17. The substrate processing method according to claim 16, furthercomprising: disposing an ion exchanger in the holding portion of theelectrode section.
 18. The substrate processing method according toclaim 17, wherein said ion exchanger has water-absorbing properties. 19.The substrate processing method according to claim 17, wherein said ionexchanger has one or both of an anion-exchange ability and acation-exchange ability.
 20. The substrate processing method accordingto claim 16, wherein said liquid is pure water, a liquid having anelectric conductivity of not more than 500 μS/cm, or an electrolysissolution.
 21. The substrate processing method according to claim 20,wherein said pure water is ultrapure water.
 22. The substrate processingmethod according to claim 16, wherein the peripheral portion of thesubstrate is a bevel portion of the substrate.
 23. The substrateprocessing method according to claim 22, wherein the bevel portion ofthe substrate is a region several mm wide extending inward from aperipheral end of the substrate.
 24. The substrate processing methodaccording to claim 16, wherein said arranging comprises arranging an endof the substrate to face the electrode section.
 25. The substrateprocessing method according to claim 24, wherein the electrode sectionhas a groove conforming to a sectional configuration of the peripheralportion of the substrate.
 26. The substrate processing method accordingto claim 25, wherein the groove is shaped to extend in an arc conformingwith a shape of the peripheral portion of the substrate.
 27. Thesubstrate processing method according to claim 24, wherein the electrodeportion comprises a flat plate.